Paperboard tampon applicators comprising a pair of telescoping cylinders are well known in the art. For example, Wiegner et al., U.S. Pat. No. 4,412,833; Beastall et al., U.S. Pat. No. 5,087,239; Hinzmann, U.S. Pat. No. 4,755,164; Huffman, U.S. Pat. No. 4,573,964; Whitehead, U.S. Pat. No. 4,508,531; Neilsen et al., U.S. Pat. No. 5,683,358; and Iskra et al., U.S. Pat. No. 5,702,553 all teach various aspects of these applicators.
Tampon applicators, whether paperboard or plastic, generally incorporate surface features at the rear or gripper end to allow the user to more or less securely hold the applicator while ejecting the tampon from the opposite end of the applicator. While molded plastic applicators can generally have pronounced gripper ends by nature of their fabrication, the gripper end configuration of paperboard applicators and applicators formed from other sheet-like materials is more limited. For example, Wiegner et al. Leaches a lightly grooved grip; Beastall et al. teaches a series of more pronounced grooves forming rings in the gripper end; Hinzmann discloses both a grip area having a reduced diameter and surface indentations; and Whitehead and Huffman both teach finger grip areas having substantially reduced diameter. Each of the finger grips taught in this prior art has a limited ability to prevent finger slip during ejection of the tampon.
More recent efforts have focused on using spinning techniques to manufacture outwardly disposed rim features. For example, Neilsen et al. discloses an apparatus for forming an outwardly projecting, integral fingergrip ring on a tampon applicator. One member of the apparatus rotates with respect another to form the curl. Iskra et al. discloses a method of fabricating paperboard tampon applicators having a diameter of less than about 25 mm and having an outwardly rolled finger grip. These techniques are similar and may offer very pronounced raised features on the tubular tampon applicator elements. However, both suffer from greatly increased mechanical complexity as they require simultaneous rotation and linear movements, the surface friction generated during the process can damage the surface of the materials, and the spinning techniques require significant clamping force to resist the rotational forces applied to the workpiece. Finally, these outwardly rolled products expose their, usually, unfinished inside surface to view in the rim. Neilsen et al. also illustrates in inwardly spun rim. This process fails to provide any raised feature while is suffers from most of the disadvantages described above. The complexity inherent in and the high frictional forces generated in the spinning processes results in higher capital equipment costs and increased likelihood of relatively high levels of scrap generation. Clearly, these traits are not desirable in a manufacturing process for low-cost products such as tampon applicators.
Therefore, what is needed is a robust, simple process for applying a rim to a tubular workpiece that generates an acceptable, low-cost product without requiring added heat energy (or dissipation thereof), and without the high axial loading caused by the rotational movement.